Rollup merge of rust-lang#90667 - rukai:improve_static_lifetime_diagn…

…ostics, r=estebank

Improve diagnostics when a static lifetime is expected

Makes progress towards rust-lang#90600

The diagnostics here were previously entirely removed due to giving a misleading suggestion but if we instead provide an informative label in that same location it should better help the user understand the situation.

I included the example from the issue as it demonstrates an area where the diagnostics are still lacking.
Happy to remove that if its just adding noise atm.

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -123,6 +123,11 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                 new_ty.to_string(),
                 Applicability::Unspecified,
             );
+        } else {
+            diag.span_label(
+                new_ty_span,
+                &format!("{} does not have lifetime `'static'`", span_label_var),
+            );
         }
 
         Some(diag)

src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.stderr

@@ -1,6 +1,8 @@
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/closure-bounds-static-cant-capture-borrowed.rs:5:5
    |
+LL | fn foo(x: &()) {
+   |           --- the type of `x` does not have lifetime `'static'`
 LL |     bar(|| {
    |     ^^^ lifetime `'static` required
 

src/test/ui/generator/generator-region-requirements.stderr

@@ -1,6 +1,9 @@
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/generator-region-requirements.rs:12:51
    |
+LL | fn dangle(x: &mut i32) -> &'static mut i32 {
+   |              -------- the type of `x` does not have lifetime `'static'`
+...
 LL |             GeneratorState::Complete(c) => return c,
    |                                                   ^ lifetime `'static` required
 

src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr

@@ -1,18 +1,24 @@
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/projection-type-lifetime-mismatch.rs:17:5
    |
+LL | fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
+   |         ------------------------------- the type of `x` does not have lifetime `'static'`
 LL |     x.m()
    |     ^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/projection-type-lifetime-mismatch.rs:22:5
    |
+LL | fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
+   |                                       -- the type of `x` does not have lifetime `'static'`
 LL |     x.m()
    |     ^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/projection-type-lifetime-mismatch.rs:27:5
    |
+LL | fn h(x: &()) -> &'static () {
+   |         --- the type of `x` does not have lifetime `'static'`
 LL |     x.m()
    |     ^^^^^ lifetime `'static` required
 

src/test/ui/issues/issue-46983.stderr → src/test/ui/lifetimes/issue-46983-expected-return-static.stderr

@@ -1,6 +1,8 @@
 error[E0621]: explicit lifetime required in the type of `x`
-  --> $DIR/issue-46983.rs:2:5
+  --> $DIR/issue-46983-expected-return-static.rs:2:5
    |
+LL | fn foo(x: &u32) -> &'static u32 {
+   |           ---- the type of `x` does not have lifetime `'static'`
 LL |     &*x
    |     ^^^ lifetime `'static` required
 

src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.rs

@@ -0,0 +1,14 @@
+use std::cell::RefCell;
+use std::io::Read;
+
+fn main() {}
+
+fn inner(mut foo: &[u8]) {
+    let refcell = RefCell::new(&mut foo);
+    let read = &refcell as &RefCell<dyn Read>;
+
+    read_thing(read);
+    //~^ ERROR explicit lifetime required in the type of `foo` [E0621]
+}
+
+fn read_thing(refcell: &RefCell<dyn Read>) {}

src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr

@@ -0,0 +1,12 @@
+error[E0621]: explicit lifetime required in the type of `foo`
+  --> $DIR/issue-90600-expected-return-static-indirect.rs:10:16
+   |
+LL | fn inner(mut foo: &[u8]) {
+   |                   ----- the type of `foo` does not have lifetime `'static'`
+...
+LL |     read_thing(read);
+   |                ^^^^ lifetime `'static` required
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0621`.

src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.stderr

@@ -1,6 +1,8 @@
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/region-lbr-anon-does-not-outlive-static.rs:9:5
    |
+LL | fn foo(x: &u32) -> &'static u32 {
+   |           ---- the type of `x` does not have lifetime `'static'`
 LL |     &*x
    |     ^^^ lifetime `ReStatic` required
 

src/test/ui/nll/guarantor-issue-46974.stderr

@@ -12,6 +12,9 @@ LL |     *x
 error[E0621]: explicit lifetime required in the type of `s`
   --> $DIR/guarantor-issue-46974.rs:15:5
    |
+LL | fn bar(s: &Box<(i32,)>) -> &'static i32 {
+   |           ------------ the type of `s` does not have lifetime `'static'`
+LL |     // FIXME(#46983): error message should be better
 LL |     &s.0
    |     ^^^^ lifetime `'static` required
 

src/test/ui/regions/regions-static-bound.migrate.stderr

@@ -14,12 +14,17 @@ LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
 error[E0621]: explicit lifetime required in the type of `u`
   --> $DIR/regions-static-bound.rs:14:5
    |
+LL | fn error(u: &(), v: &()) {
+   |             --- the type of `u` does not have lifetime `'static'`
 LL |     static_id(&u);
    |     ^^^^^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `v`
   --> $DIR/regions-static-bound.rs:16:5
    |
+LL | fn error(u: &(), v: &()) {
+   |                     --- the type of `v` does not have lifetime `'static'`
+...
 LL |     static_id_indirect(&v);
    |     ^^^^^^^^^^^^^^^^^^ lifetime `'static` required
 

src/test/ui/regions/regions-static-bound.nll.stderr

@@ -9,12 +9,17 @@ LL |     t
 error[E0621]: explicit lifetime required in the type of `u`
   --> $DIR/regions-static-bound.rs:14:5
    |
+LL | fn error(u: &(), v: &()) {
+   |             --- the type of `u` does not have lifetime `'static'`
 LL |     static_id(&u);
    |     ^^^^^^^^^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `v`
   --> $DIR/regions-static-bound.rs:16:5
    |
+LL | fn error(u: &(), v: &()) {
+   |                     --- the type of `v` does not have lifetime `'static'`
+...
 LL |     static_id_indirect(&v);
    |     ^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required